The performance of cutting tools can often be improved by lubricating the work or the cutting element. In regard to glass, for example, lubricaton produces smoother and more precise operation, and helps to prevent flaking along the score line; it is particularly advantageous for cutting stained glass elements. In mechanical systems, lubrication may also serve a cooling function, thereby avoiding overheating and maximizing the useful life of the tool.
The desirability of providing a reservoir of a liquid lubricating substance for such a cutting device has long been recognized. In Fells U.S. Pat. No. 778,023, for example, a manual glass cutter is disclosed which consists of a hollow body connected to a head on which the cutting wheel is mounted. The head has a bore providing communication between the cutting wheel and the oil reservoir provided by the hollow body, and a wad of cotton or the like may be used to filter the lubricant. In one emoodiment, the bore of the head member is closed by a valve which is operated by a threaded knob at the end of the handle. In a second case, the handle has a small port located under a threaded cap; displacement of the cap will permit air to pass through tne port, and will thereby allow the oil to flow into the bore.
A device somewhat similar to that of the Fells Patent is disclosed by Rivard in U.S. Pat. No. 2,042,965. He utilizes, however, a stop-cock to control the admission of air and escape of fluid through a passageway to the cutting element, and applies his concepts to roofers knives as well as to rotary cutting instruments. Another similar device is shown in Belgian Pat. No. 566170, and Kurtz et al disclose, in U.S. Pat. No. 1,606,802, a glass cutter having a separate lubricator mounted upon the holder, with a wick to apply the lubricating fluid to the work.
The advantages of providing, in such so-called "oil cutters", means for automatically releasing controlled amounts of lubricant during normal cutting operations have also been recognized. One early device of this nature, disclosed by Hornig in U.S. Pat. No. 989,603, has a separate reservoir from which the lubricant is dispensed, through contact of a shank upon the work, as the cutter is moved along it. In addition, glass cutters having a pressure-responsive oil feed feature as well as a self-contained reservoir are shown in U.S. Pat. Nos. 4,110,907 and 4,287,699, to Einhorn et al and Arai, respectively, and in German Offenlegungsscrift No. 1,940,442. Madge U.S. Pat. No. 3,136,191 discloses a head for a glass cutting machine providing such a lubricating feature.
The prior art also discloses other types of devices for dispensing a variety of liquid substances, in response to manual force. Aune shows a fountain oiler in U.S. Pat. No. 925,794; Hurt shows an oil can in U.S. Pat. No. 947,991; a fountain marking device is disclosed by Soldner in U.S. Pat. No. 2,624,902; and a soap dispenser is disclosed by Herman et al in U.S. Pat. No. 2,939,613.
Glass cutters having a self-contained oil supply have also been offered commercially in the past. One such device consists of a hollow body for containing the lubricant, and a cutting head attached to the body by a rod. The rod simultaneously operates a pair of valves, when the head is depressed against the workpiece; one valve permits the flow of oil from the reservoir, and the other controls the admission of air.
Despite the foregoing, a need remains for a simple, pressure-responsive cutting device having a self-contained supply of lubricant, which consists of a minimum number of parts and is nevertheless highly convenient and efficient in use.
Accordingly, it is an object of the present invention to provide a novel cutting device capable of discharging lubricant to the cutting element in response to normal operating pressure, which is of relatively uncomplicated design, consists of a minimal number of parts, and is highly convenient, neat and effective to use.
It is a more specific object of the invention to provide a manual glass cutter having the foregoing features and advantages, wherein the supply of lubricant to the cutting element is reliable, and any dripping or leakage is minimized or avoided.
It is also an object of the invention to provide such a device which is relatively facile and inexpensive to manufacture.